Manufacture of solid carbon dioxide



Aug. 21, 1934. R. L. HASCHE 1,971,106

MANUFACTURE OF SOLID CARBON DIOXIDE Filed Jan. 31. 1930 H II I' I Hi INVENTOR B00701]!!! lmnardfiaseize 1 ATTORNEY Patented Aug. 21, 1934 PATENT OFFICE MANUFACTURE OF SOLID CARBON DIOXIDE Rudolph Leonard Hasche, Tacoma, Wash., as-

signor to Carbonic Development Corporation, a corporation of Delaware Application January 31,

Claims.

The invention relates in general to the separation of gases from gaseous mixtures, and more particularly, to the manufacture of solid carbon dioxide from a gaseous mixture containing 5 carbon dioxide.

According to one form of practicing the invention the source of carbon dioxide may be the gases resulting from the' combustion of coal, coke, wood, charcoal, oil or other carbonaceous material. Under favorable (conditions a gaseous mixture containing from to 18% carbon dioxide by volume may be thus obtained.

According to the invention the gaseous mixture may be compressed to from 40 to 50 atmospheres pressure and then cooled by refrigeration until the carbon dioxide is liquefied. The refrigeration may be obtained from the unliquefied compressed gases which maybe expanded in an expansion engine to obtain a very low tem- 20 perature.

The liquid carbon dioxide is recovered at a very low temperatureand at a comparatively low partial pressure. The liquid carbon dioxide at this low temperature and under the head ,25 pressure of the unliquefled gases is throttled into an expansion chamber to change the liquid carbon dioxide into solid carbon dioxide.

A further feature of the invention is the provision of a second circuit consisting of a second compressor driven by the expanding engine to reliquefy the carbon dioxide unchanged to solid in the expansion chamber. This liquefied carbon dioxide may be cooled and may be added to that obtained from the main liquefaction circuit. If desired, a portion of the liquid carbon dioxide obtained in the second circuit may be used for cooling an auxiliary cold storage chamber.

Various other features and advantages of the 40' invention will be apparent from the following particular description and from an inspection of the accompanying drawing.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection withthe acccigipanying drawing forming a part thereof, in w ch V The single figure represents diagrammatically a system according to the invention. In the following description and in the claims 1930, Serial No. 424,773 (01. 62-121) the various steps in the process and the details comprising the invention will be identified by specific names for convenience but they are intended to be as generic in their application as the art will permit. I

Referring now to the drawing, gas containing say 15% to 18% of carbon dioxide, which has been freed by a suitable cleaning treatment from sulphur compounds and other objectionable impurities, is drawn through pipe 1 into compressor 65 2 in which it is compressed to a pressure of from 40 to 50 atmospheres. The gas is cooled by water' ,in heat exchanger 3 and dried by passage through driers 4 and 5 which contain a drying agent such as silica gel. These driers 4 and 5 operate alternately, the gas passing through one until approximately the saturation point is reached, the gas then being shifted to the other drier and the first one activated by passage of hot air through the silica gel. It will be understood that the arrows in the drawinglrepresent the direction of flow of material.

From the driers 4 and 5 passes through the tubes of exchangers 6 and 7 which operate in parallel, the amount of gas passing through each exchanger being so regulated by valves 8 and 9 that the maximum refrigeration is obtained from the cold gas (obtained as hereinafter described) flowing upwards in the shell compartments of the respective exchangers. During passage of the compressed gas downwards through exchangers 6 and 7 it is cooled to a temperature sufiiciently low to condense out some liquid carbon dioxide.

The cold compressed gas and liquid passes downwards through the tubes of exchanger 8' wherein further cooling takes place (as hereinafter described), resulting in the liquefaction of further quantities of liquid carbon dioxide. This liquid, corresponding in amount to about 80% of the carbon dioxide contained in the inlet gas, is drawn out, at a temperature of about F.

into tank 9 from which it passes to expansion chamber 10, expanding through one or more nozthe compressed gas zles indicated by 11. 100

Cold compressed stripped gas,from which the greater part of its carbon dioxide content has been liquefied leaves exchanger 8' through pipe 12 and passes upwards through the shell compartment of exchanger 7, tion to incoming gas. Thence it passes through pipe 13 into expanding engine 14 wherein, at the expense of external work, the gas is cooled to a very low temperature. It is important that the cut-off on the engine be so regulated as to pro- 110 giving up its refrigeraduce the correct amount of expansions to prevent the formation of solid carbon dioxide within the engine cylinder, and yet attain a sufiiciently low temperature to give the desired amount of refrigeration.

From the expander 14, the gas at a temperature of about l80 F. passes through pipe 15 upwards in turn through theshell compartments of exchangers 8' and 6 respectively and, after giving up its refrigeration in cooling incoming gas and liquefying carbon dioxide therefrom, is vented to the atmosphere through pipe 16.

To take fullest advantage of the energy and refrigeration available in the process a second cycle may be provided. During the expansion of liquid carbon dioxide in chamber 10 to produce the solid there is a considerable portion of the carbon dioxide which leaves the chamber as a gas. This passes out through pipe 1'1 into the shell of exchanger 18, wherein a portion of the liquid carbon dioxide passing through its tubes (obtained as herein described) is sub-cooled.

The gas then passes through pipe 19 into a small three stage compressor 30 in which it is compressed to about 60 atmospheres. This compressor is driven by power from the expanding engine 14 as through belt 31. The pure carbon dioxide gas after compression passes through pipe 20 to water cooled coil 21, wherein liquefaction occurs, the liquid collecting in pot 22. The liquid in pot 22 may pass through the tubes of exchanger 18 where it is sub-cooled to a low temperature by the gas flowing through the shell of exchanger 18 and joins the liquefied portion from the first liquefaction system in tank 9.

If desired, the liquid in pct 22 may pass through expansion valve 23 and through expansion coils 24 for cooling the cold storage room 25 and thence pass through relief valve 26 and enter the second stage suction manifold of compressor 30.

An optional method of utilizing some or the waste carbon dioxide from the expansion chamber 10 is to introduce a portion through pipe 26' into the primary compressor 2 to be recirculated through the primary liquefaction system.

Thus a carbon dioxide system is provided which has great efficiency. It .has been found that the percentage of liquid carbon dioxide, passing into the solid form upon expansion, increases as the temperature of the liquid is lowered. However, as the temperature 0! the liquid is lowered, its vapor pressure also decreases, so that it is necessary to maintain a pressure on the liquid by unliquefied inert gases in order to force the required amount of carbon dioxide through the expansion valves. the compressed, refrigerated, unliquefied gases to cool the incoming compressed gases. The provision of an expansion engine secures a much lower temperature by expanding the compressed unliquefied gases by making them do external work. This energy obtained is put to useful advantage by driving the secondary compressor which reliquefies the carbon dioxide which vaporizes in the expansion chamber.

. While certain novel features of the invention have been shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

1. The method oi! making solid carbon dioxide which comprises compressing a mixture of carbon dioxide and other gases to the neighborhood 0! Furthermore, use is made of 40 to 50 atmospheres total pressure, cooling the mixture to the neighborhood of F. to cause the carbon dioxide to liquefy, the partial pressure of the carbon dioxide dropping to a value corresponding to the vapor pressure at that temperature while keeping the total pressure substantially constant, separating the unliquefied gases from the liquid carbon dioxide, throttling substantially all the liquid carbon dioxide at reduced temperature to substantially one atmosphere total pressure to form solid carbon dioxide and using the unliquefied gases as the sole cooling agent for cooling the compressed mixture below ordinary temperatures.

2. The method of making solid carbon dioxide which comprises compressing a mixture of carbon dioxide and other gases, cooling the mixture below ordinary temperatures to cause the carbon dioxide to liquefy and its partial pressure to drop while keeping the total pressure constant, separating the unliquefied gases from the liquid carbon dioxide, throttling the liquid carbon dioxide at reduced temperature to form solid carbon dioxide and using said unliquefied gases as the sole cooling agent for cooling the compressed 1 mixture below ordinary temperatures.

3. The method of separating carbon dioxide from other gases which comprises compressing the mixture and cooling it to liqueiy the carbon dioxide, using the unliquefied, cooled gases to cool the incoming mixture, then expanding the unliqefied somewhat warmed resulting gases and then using the expanded gases to further cool the incoming mixture.

4. A system for making liquid carbon dioxide comprising a compressor for compressing a mixture of carbon dioxide and other gases, a first stage heat exchange device for cooling the compressed mixture of gases, said first heat exchange device consisting of first and second parts connected in parallel, a second stage heat exchange device for further cooling the compressed mixture of gases to liqueiy the carbon dioxide, a receiver for holding the liquid carbon dioxide, means for circulating unliquefied refrigerated gases from said second stage to cool said first part of said first stage, means for expanding said unliquefied gases leaving the first stage and using them to cool said second stage, and means for using the expanded gases leaving said second stage to cool said second part of said first stage.

5. A system for making liquid carbon dioxide comprising a main compressor for compressing a mixture of carbon dioxide and other gases, a first stage heat exchange device made up of a first and second part in parallel for cooling the compressed mixture oi. gases, a second stage heat exchange device for further cooling the compressed mixture of gases to liqueiy the carbon dioxide, 9. receiver for holding the liquid carbon dioxide, means for circulating unliquefied reirigerated gases from said second stage to cool said first part 01' said first stage, a driving engine receiving said unliquefied gases leaving the first stage to drive said engine, means for leading the exhaust of said engine to said second stage to cool it, and means for leading said exhaust leaving said second stage to cool said second part of said first stage.

6. A system for making dry ice comprising a main compressor for compressing a mixture of carbon dioxide and other gases, 9. first stage heat exchange device for coolin the compressed mixture of gases, 2. second stage heat exchange deviceiorturther eoolingthe compressedmixturc of gases to liquefy the carbon dioxide, a receiver for holding the liquid carbon dioxide, means for circulating unliquefled refrigerated gases from said second stage to cool part of said first stage, a driving engine receiving said uniiquefled gases leaving the first stage to drive said engine, means for leading the exhaust of said engine to said second stage to cool it, and means for leading said exhaust leaving said second stage to cool another part of said first stage, an expansion chamber for expanding the liquid carbon dioxide to form solid carbon dioxide, a secondary com-' pressor driven by said engine for compressing the gas from said expansion chamber. and means for liquefying said compressed gas from said expansion chamber.

7. The method of making solid carbon dioxide as a continuous process which comprises compressing gaseous carbon dioxide from an external source, cooling the same by refrigeration generated within the system to liquefy it and then expanding such liquid carbon dioxide while at such reduced refrigeration temperature into the solid form. I

8. The method of liquefying gaseous carbon dioxide which comprises compressing a gas inreduced refrigerating temperature thereof, using the stripped unsolidified gases to cool the incoming mixture and expanding the refrigerated liquid carbon dioxide into solid form while at such reduced refrigeration temperature.

10. The method of making solid carbon dioxide which comprises maintaining liquid carbon dioxide at refrigerating temperature, maintaining the liquid carbon dioxide at a pressure greater than its vapor pressure by an inert gas and expanding such liquid carbon dioxide while at such reduced refrigeration. temperature into the solid RUDOLPH LEONARD HASCHE. 

